Caterpillars outsmart birds

Yes, they are smart enough to beat birds. Caterpillars that masquerade as twigs to avoid becoming a bird's dinner are actually using clever behavioural strategies to outwit their predators, a new study reveals.

Dr. John Skelhorn, a lecturer in animal behaviour at the University of Exeter, said: "The caterpillars are not just blindly mimicking inedible objects in the environment and hoping for the best, they are actually using complex habitat-selection strategies which exploit predators' hunting behaviour. According to the study, twig mimicking ‘Early Thorn moth’ caterpillars (Selenia dentaria) choose their location to maximise their chances of fooling their predators into thinking they are twigs.

Using domestic chicks (gallus gallus domesticus) as predators of the caterpillars, research showed that caterpillars are more likely to fool birds when twigs are common. In order to exploit birds' behaviour, caterpillars position themselves in locations where twigs are in abundance during the day -- even if they're not good locations for feeding. At night, when the predators cannot hunt by sight, the caterpillars go to rich feeding grounds -- regardless of twig abundance.

Study reveals that chicks are less likely to search for masquerading prey when the object they mimic, in this case twigs, is in abundance.

"The caterpillars make the most of this by selecting habitats where twigs are common during the day, but then abandon them at night, when there are no visually-hunting predators around, in order to go in search of the best feeding grounds."

When the caterpillars were given two options; one with few twigs but plenty of food, and another with more twigs but no food, Caterpillars showed a strong preference for the branch with lots of twigs, offering the best protection from their predators, during the daylight. At night, they opted for the food-rich branch.

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Caterpillars aren’t so bird brained after all

John Skelhorn, Hannah M. Rowland, Jon Delf, Michael P. Speed, Graeme D. Ruxton. Density-dependent predation influences the evolution and behavior of masquerading prey. Proceedings of the National Academy of Sciences, 2011; DOI: 10.1073/pnas.1014629108

FOGSL’s Field visit to the Delft Island

The Field Ornithology Group of Sri Lanka (FOGSL) organized a field tour to Jaffna Peninsula and surrounding islands from 16-20th February 2011, with the participation of 29 of its members. Scheduled for the day three of this trip was a birding tour to Delft Island, locally known as Neduntheevu. It is the largest island (45 km2) in the Palk Strait, located about 40 km off Jaffna peninsula. The only other land mass beyond this is the Kachchativu, which is a barren island positioned at the border of the maritime boundary of Sri Lanka. Delft was named after a city in Holland during the Dutch colonial rule of the country. Unspoilt and untouched by modernity, mainly due to civil unrest during the last 30 odd years, Delft island offers a wide experience to the traveler in the form of birds, wild ponies, old forts, Baobab trees and beautiful beaches.

We boarded the ferry from Kurikadduwan jetty in Punkudutiv island around 8.30 in the morning and reached Delft after more than one hour of sea journey. Several of us opted to sit on the roof of the ferry as the sea was calm as a lake and watched sea gulls and Brahminy kites freely roaming above us. Striated heron was the first bird to be spotted on the nearby shore of the island. It was interesting to watch the antiques of this bird as it got ready to pounce on its prey. These birds are known to place baits such as feathers or leaves on the water surface and pick fish that come to investigate

After having a quick breakfast of ‘sinisambal’ and bread, we found two ‘land masters’ with the assistance of the Navy officials. These small tractors are the main transportation method in Delft and there is single CTB bus operating on scheduled time periods. Thankfully the land is flat, but you have to endure a bumpy ride in the rough terrain under a very hot sun with only Palmyra palms and few dry shrubs for shade. A lonely Indian roller was encountered in an old Dutch church yard near to the navy camp. The beauty of this bird can be only seen during its flight when striking shades of blue mixed with brown can be witnessed. Next bird to be spotted was a Red collared dove, which is related to more commonly seen spotted dove.

The splendor of the dashing wild ponies mesmerized all of us for quite a while. These animals are not native to Sri Lanka, but are a legacy left behind by the colonial rulers including the Portuguese, the Dutch and the British, who bred the animals for transport and work. Some of the animals are branded indicating that their “wild status” is no longer valid. The literature says that during droughts these ponies have a hard time finding enough water to survive and that due to increase in the number of domesticated cattle, there is a competition for food . The remoteness and inaccessibility of the island has provided protection to the wild ponies to live and breed freely up to now, yet in future with the influx of more people, conservation measures will be needed to ensure their survival. Our next stop was a large water hole where an aggregation of waders including Black winged stilts and ducks such as Garganey and Northern Pintail were observed. In the background several wild ponies were quenching their thirst while a young colt was happily playing about.

The giant Baobab tree is another land mark not to be missed. We spent more than fifteen minutes under the shade of the tree, which was a welcoming relief from the very hot sun. Like the Mannar Baobab, this tree was most probably introduced by the Arabian traders. For lunch we purchased biscuits and soft drinks from the small village boutique located near the Kytes tourist court house. Around 5,000 people inhabit the island and they live in small compounds separated from each other by walls built up of dead coral. One has to walk through the small Government Hospitals corridor to have a look at the ruins of the Dutch Fort. Beyond this fort is a cemetery where you will find tomb stones belonging to all religions. During the colonial rule, carrier pigeons were used as the medium of communication between the islands and there still evidence for this in the form of stone cote.

During the few hours we spend at the Delft island, we observed 64 bird species. A multitude of butterfly species are also found in the island and several of us got busy photographing them. Spending five hours was grossly inadequate to fully appreciate the wonders of this delightful small island and its friendly people. Yet due to time constrains, we had to leave it behind with the hope of visiting again, someday soon.

The Department of Wildlife Conservation has identified part of the Delft to be declared as a National Park under the Flora and Fauna Protection Ordinance, mainly to protect to wild ponies. This came as a recommendation under the project titled Integrated Strategic Environment Assessment for the Northern Province. Although good in intention, the technical and financial feasibility of this action is doubtful and a more appropriate action would be to declare the whole island as an Environmental Sensitive Area under the National Environment Act and thereafter develop guidelines to promote sustainable development initiatives within the island. It is also highly relevant to carry out a species and habitat assessment of the island before any such regulations are established.

Bird List

Lesser Whistling-duck

Eurasian Wigeon

Garganey

Little Grebe

Asian Openbill

Black-headed Ibis

Eurasian Spoonbill

Striated Heron

Indian Pond-heron

Cattle Egret

Grey Heron

Great Egret

Intermediate Egret

Little Egret

Spot-billed Pelican

Little Cormorant

Indian Cormorant

Black Kite

Brahminy Kite

White-bellied Sea-eagle

Shikra

White-breasted Waterhen

Black-winged Stilt

Yellow-wattled Lapwing

Red-wattled Lapwing

Common Ringed Plover

Little Ringed Plover

Black-tailed Godwit

Common Redshank

Marsh Sandpiper

Common Greenshank

Wood Sandpiper

Common Sandpiper

Ruddy Turnstone

Little Stint

Curlew Sandpiper

Brown-headed Gull

Gull-billed Tern

Caspian Tern

Whiskered Tern

Rock Pigeon

Eurasian Collared-dove

Spotted Dove

Rose-ringed Parakeet

Asian Koel

Greater Coucal

Asian Palm-swift

Indian Roller

White-throated Kingfisher

Common Kingfisher

Little Green Bee-eater

Blue-tailed Bee-eater

Ashy Woodswallow

Black Drongo

House Crow

Jungle Crow

Barn Swallow

Oriental Skylark

Red-vented Bulbul

Common Myna

Pale-billed Flowerpecker

Purple Sunbird

House Sparrow

Paddyfield Pipit


Report and Photographs: Nishanthi Perera

An Encounter with the Little Penguins at the Phillip Islands Nature Parks

Located 90 minutes drive from the city of Melbourne, the not-for-profit ‘Phillip Island Nature Parks’ is the renowned home of Australia’s most popular natural wildlife attraction, the iconic Penguin Parade, where during every sunset hundreds to over a thousand wild Little Penguins (Eudyptula minor) emerge from the sea and march across the beach to their sand dune burrows. It is the best place in the world to experience this completely natural phenomenon and I have been fortunate enough to witness it twice during my visits to Australia.

 

The Little Penguin is the smallest of 17 species of penguins recorded; growing to only 35 cm or 13 inches and the adult weighs just over one kilogram. In comparison the Emperor Penguin, this is the largest penguin in the world, stands over 110 cm and can weigh 30 kg. The Little Penguin is the only Penguin to breed in Australia. Its dark feathers are not black like other penguins. They are a deep rich blue. Their colour camouflages them from above and below the surface of the ocean. Only males undertake burrow construction. Courtship follows, with the male seeking to impress the female with the prepared burrow. The female chooses the burrow she likes best and that male will be her mate for the year. Nest building begins around April with the first chicks emerging in June. The adults attend to the chicks until they fledge which usually begins in August. It is not uncommon for adults to raise two sets of chicks so there are chicks in the colony until January. Following nesting the adults go out to sea to feed prior to the moulting season, which occurs between December and February. Moulting is followed by another feeding period prior to commencing breeding again. Summerlands Peninsula on the south-western coast of Phillip Island is home to over 28,000 breeding Little Penguins making it one of the largest colonies of that species in the world.

The Phillip Island Nature Parks is part of the UNESCO Mornington Peninsula and Western Port Biosphere Reserve and encompasses wildlife sanctuaries, wetlands, woodlands and breathtaking coastlines which are protected and managed by quality environmental and research programs. Other than being a home to a significant population of Little Penguins it also hosts Hooded Plovers, Short-tailed Shearwaters, and other migratory bird species and mammals such as koalas, possums, wallabies, Australian Fur Seals and bats. The Parks also protects a range of plant communities which includes over 330 native species. Sections of the Nature Parks also fall within or are adjacent to wetlands protected under the intergovernmental Ramsar Convention as wetlands of international importance.

Created by the State Government in 1996, the Phillip Island Nature Parks is the only ‘Nature Park’ in Victoria. The term means that all conservation areas (1, 805 ha or 25% of the island) are managed under the Crown Land (Reserves) Act 1978 and is managed by a Board of Management that is appointed by the Minister responsible for the Crown Land (Reserves) Act 1978. The Nature Parks’ vision is to be a world leader in environmental, economic and socially sustainable nature based and ecotourism experiences. The Nature Parks does not receive ongoing funding from the state or federal government and is self-funded by revenue generated from four main attractions (Penguin Parade, Koala Conservation Centre, Churchill Island Heritage Farm and Nobbies Centre) the Parks was visited by around 1 million people in 2009/10. These visitors came from both around Australia (48%) and internationally (52%). According to an independent economic impact study, the Nature Parks contributes AUD $107 million dollars per annum in direct expenditure to the Victorian economy and AUD $56 million per annum in indirect expenditure. Since the formation of the Nature Parks, funds raised through its commercial operations has been used to protect Phillip Island’s wildlife and their habitat. Conservation projects the Nature Parks undertakes include re-vegetation, habitat restoration, eradication of feral animals and wildlife rehabilitation. In 2009/10, over 60,000 trees were planted on Phillip Island through Nature Parks’ programs. It has an exciting volunteer program which is open to the public, in which the volunteers can assist the Nature Parks with conservation, environment and education projects. Further the Penguin Foundation provides dedicated source of funding for penguin research, rehabilitation, and protection and rescue projects to ensure the ongoing survival of the Little Penguin colony on Phillip Island. By Adopting a Penguin, becoming a Foundation member or making a donation, people have the opportunity to follow the life of a Little Penguin and to play an important role in the conservation of these unique creatures.

Acknowledgment: Ms Sue Davies, Communications Executive of the Phillip Island Nature Parks for providing inputs and photographs of penguins, as photography is prohibited outside the visitor center at the Penguin Parade. More information can be obtained from http://www.penguins.org.au/.

Reported by Nishanthi Perera